In general, virtual reality is one of user interface technologies that allows a user wearing special glasses or the like to experience what is possible inside the software program of a computer as if he or she is experiencing it in real life through the human sense such as vision, hearing, or the like.
In order to realize this technology, a treadmill or the like may be used for providing a participant of the virtual reality with actual walking or running motion.
However, although it is possible to realize the actual walking or running motion of the participant, it is not possible to realize certain environment such as microgravity environments such as those on the moon or Mars. For reference, an environment is usually said to have the ‘microgravity’ when it has a gravity but that gravity is so weak to a negligible extent.                Prior art document: U.S. Pat. No. 6,152,854 (Nov. 28, 2000)        